Sloppy vertical scrolling when graphs are zoomed out to maximum time range. Glitchy animations when filtering graphs #3 and #5.

Bar chart has bad animations: empty spaces in the middle of the chart.

Local min is always zero on the first chart

Scrolling while touching down (u have to hold the touch down in order to see the tooltip) introduces a white background view on the tooltip

— Upper bound values are cut when scaling. 
— The app is slow and blinks when scaling and filtering the third and fifth charts.
— iOS 11+ only.

labels on the percentage chart update in the same fashion as on all the other charts

Look at the right

Line chart has no y-axis animations.

Switching theme doesnt change the tooltip label color

Labels on the tooltip are cut off + bigger white line on charts with more series

Unwanted animation after the start

Does not support iOS 8. Telegram does.

Major issue: does not support iOS 10.

Critical issue: lines are a lot thinner than it needs to be. Thus this contestant has major advantage in performance over other participants or just hides drawing artifacts (because he uses Metal)

line joints are changing during the movement

can't activate new filter until the animation of the previous one is finished

Vertical and horizontal scrolls do not cancel each other. It's not user-friendly when you select the dates with tooltip

date and y-value labels are not animated in most cases.

poor scrolling performance on iPhone 6+. 30-40 fps

Critical issue: Line joints are not rounded, even on iPhone X. So, it's not some minor optimization for old devices, rounded joints implementation on Metal require a lot more math to implement, a lot more vertices to calculate for each frame and 2-3 times more polygons to draw.

Critical issue: This code uses Metal and it will never work on 32-bit devices (including iPhone 5 on iOS 10.3).

Major issue: It's not so easy to port this code to iOS 8 on iPhone 5S either, because he uses help classes from MetalKit (otherwise he would support iOS 8). And you have to do a lot more work without it.

Critical issue: line drawing quality is poor. It is not easy to implement good line quality on bare Metal, MSAA is not enough. Qualitative line drawing requires a lot more calculations and tricks. And such implementations may still be worse than Core Animation / Core Graphics quality and would definitely affect the performance. You can read more about line quality in Metal projects in my comments on entry228.